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QLDPhysicsQuick questions
Unit 4: Revolutions in modern physics
Quick questions on Quantum theory: photons, the photoelectric effect and atomic spectra (QCE Physics Unit 4)
7short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is threshold frequency?Show answer
This is the minimum frequency at which the photoelectric effect occurs.
What is stopping voltage?Show answer
The retarding voltage that stops all photoelectrons is the stopping voltage:
What is emission spectra?Show answer
Hot, low-density gas emits photons during electron transitions to lower levels. Bright lines on dark background, each line a specific wavelength.
What is absorption spectra?Show answer
Continuous light passes through cool gas; specific wavelengths are absorbed. Dark lines on bright continuous spectrum.
What is q1?Show answer
State the photoelectric equation and define each term. [2 marks]
What is q2?Show answer
Calculate the energy of a photon in joules and eV. [3 marks]
What is q3?Show answer
A photoelectric cell uses sodium () illuminated at . (a) Calculate the photon energy and the stopping voltage. (b) Determine the threshold frequency for sodium.
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